On Wed, Jan 26, 2011 at 1:35 PM, Kathleen Fisher
~/.cabal/bin/cabal install -w ~/sw/ghc-7.01/bin/ghc --package-db=/Users/kfisher/sw/ghc-7.01/lib/ghc-7.0.1/package.conf.d
I get the following error messages:
Resolving dependencies... cabal: cannot configure mainland-pretty-0.1.0.1. It requires containers =0.2 && <0.4
See here that mainland-pretty has excluded containers 0.3? That's your problem - GHC 7 ships with containers 0.4. That's question number one: why is it trying to configure a library that is
already installed?
Because it's trying, and failing, to meet a set of internally inconsistent version dependency constraints. That's the second question: why does cabal install not work while breaking
it into pieces does work?
By breaking the install into pieces, you're letting the package manager see only a small fraction of the dependency graph at a time, and those disconnected pieces of the graph are not themselves internally inconsistent. It's when cabal gets a holistic look at the lot that everything goes kablooie.